using System.Collections.Generic;
using System.Text.RegularExpressions;
public static void Main()
string[] partNumbers= { "172.16.15.1",
string pattern = @"^([1-9]|[1-9]\d|1\d{2}|2[0-4]\d|25[0-5])(\.(\d|[1-9]\d|1\d{2}|2[0-4]\d|25[0-5])){3}\/(\d|[1]\d|[2]\d|[3][0-2])$";
foreach (string partNumber in partNumbers)
Console.WriteLine("{0} {1} a valid ip address.",
Regex.IsMatch(partNumber, pattern, RegexOptions.IgnoreCase)